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Re: SuSy dynahi v2

PostPosted: June 8th, 2015, 1:42 pm
by mloutfie
Thanks for all the info guys. Really helps. Now I know both bias value are possible. Jmc and DEFL what resistor value do you guys use next to the biasing trimpot? 500ohm or 680ohm?

Re: SuSy dynahi v2

PostPosted: June 8th, 2015, 2:54 pm
by DEFL
jmc wrote:R23 and R34 are 100r on the schematics but the onboard version has 50r on the silkscreen.

And so does offboard version.
http://gilmore.chem.northwestern.edu/bo ... hibal9.zip
Strange. If Kevin meant to say that 50Ohm will physically limit bias, then I don't know how I easily reached 0.75V (and more, if I wanted to).

Re: SuSy dynahi v2

PostPosted: June 8th, 2015, 3:02 pm
by DEFL
mloutfie wrote:500ohm or 680ohm?

500Ohm.

Re: SuSy dynahi v2

PostPosted: June 8th, 2015, 3:23 pm
by jmc
DEFL wrote:
jmc wrote:R23 and R34 are 100r on the schematics but the onboard version has 50r on the silkscreen.

And so does offboard version.
http://gilmore.chem.northwestern.edu/bo ... hibal9.zip
Strange. If Kevin meant to say that 50Ohm will physically limit bias, then I don't know how I easily reached 0.75V (and more, if I wanted to).


I honestly don't know if it phisically limit bias or whatever it does, my electronics knowledge isn't that good :)
I am just reporting what he told me after I had the same issue mloutfie is having.

I am not really sure but I think I used 680r.

edit: I checked the pictures and I did use 680r. Maybe that's why we couldn't raise the bias?

Re: SuSy dynahi v2

PostPosted: July 4th, 2015, 2:02 am
by mloutfie
Finished fixing up my board today. But the best I can bias my board is 0.69v for + side and 0.71 for negative side. The offset without servo is 80mV and 10mV with servo. Is it good enough? Or I still need to get closer to 0.75v and get offset to 0? Any idea which part I need to change? Should I change the 500ohm resistor to something lower?

Re: SuSy dynahi v2

PostPosted: July 4th, 2015, 1:25 pm
by amb
I'll let others comment on the biasing, but a DC offset of 10mV is acceptable (if not great), but 80mV is too high.

Re: SuSy dynahi v2

PostPosted: July 5th, 2015, 2:07 am
by mloutfie
With the servo the offset still drift between 10-20mV is that still fine? I've tried using headphones on balanced the sound is great but on single ended the sound is sucked out especially the mids but strangely low end is fine

Re: SuSy dynahi v2

PostPosted: July 5th, 2015, 4:46 am
by amb
You might have a wiring problem -- reversed signal and ground somewhere?

Re: SuSy dynahi v2

PostPosted: July 5th, 2015, 1:04 pm
by mloutfie
On single ended I wire signal and ground to + and - of the board. And on the wiring I wire only the signal part to the headphone jack. The ground I took direct from the source ground. Does that sound correct?

Re: SuSy dynahi v2

PostPosted: July 5th, 2015, 8:27 pm
by amb
Mostly.

For unbalanced, the input RCA signal and ground should go to +In and ground, respectively. Then -in should be connected to ground too.

Also, while source ground is connected to the power supply ground via the board, you should connect the TRS jack ground (sleeve contact) directly to the power supply ground. You shouldn't let the headphone's return current current to go through the board's ground, thereby polluting it.